/**
 * @file
 * AutoIP Automatic LinkLocal IP Configuration
 *
 */

/*
 *
 * Copyright (c) 2007 Dominik Spies <kontakt@dspies.de>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 *
 * Author: Dominik Spies <kontakt@dspies.de>
 *
 * This is a AutoIP implementation for the lwIP TCP/IP stack. It aims to conform
 * with RFC 3927.
 *
 *
 * Please coordinate changes and requests with Dominik Spies
 * <kontakt@dspies.de>
 */

/*******************************************************************************
 * USAGE:
 *
 * define LWIP_AUTOIP 1  in your lwipopts.h
 *
 * If you don't use tcpip.c (so, don't call, you don't call tcpip_init):
 * - First, call autoip_init().
 * - call autoip_tmr() all AUTOIP_TMR_INTERVAL msces,
 *   that should be defined in autoip.h.
 *   I recommend a value of 100. The value must divide 1000 with a remainder almost 0.
 *   Possible values are 1000, 500, 333, 250, 200, 166, 142, 125, 111, 100 ....
 *
 * Without DHCP:
 * - Call autoip_start() after netif_add().
 *
 * With DHCP:
 * - define LWIP_DHCP_AUTOIP_COOP 1 in your lwipopts.h.
 * - Configure your DHCP Client.
 *
 */

#include "lwip/opt.h"

#if LWIP_AUTOIP /* don't build if not configured for use in lwipopts.h */

#include "lwip/mem.h"
#include "lwip/udp.h"
#include "lwip/ip_addr.h"
#include "lwip/netif.h"
#include "lwip/autoip.h"
#include "netif/etharp.h"

#include <stdlib.h>
#include <string.h>

/* 169.254.0.0 */
#define AUTOIP_NET         0xA9FE0000
/* 169.254.1.0 */
#define AUTOIP_RANGE_START (AUTOIP_NET | 0x0100)
/* 169.254.254.255 */
#define AUTOIP_RANGE_END   (AUTOIP_NET | 0xFEFF)


/** Pseudo random macro based on netif informations.
 * You could use "rand()" from the C Library if you define LWIP_AUTOIP_RAND in lwipopts.h */
#ifndef LWIP_AUTOIP_RAND
#define LWIP_AUTOIP_RAND(netif) ( (((u32_t)((netif->hwaddr[5]) & 0xff) << 24) | \
                                   ((u32_t)((netif->hwaddr[3]) & 0xff) << 16) | \
                                   ((u32_t)((netif->hwaddr[2]) & 0xff) << 8) | \
                                   ((u32_t)((netif->hwaddr[4]) & 0xff))) + \
                                  (netif->autoip ? netif->autoip->tried_llipaddr : 0))
#endif /* LWIP_AUTOIP_RAND */

/**
 * Macro that generates the initial IP address to be tried by AUTOIP.
 * If you want to override this, define it to something else in lwipopts.h.
 */
#ifndef LWIP_AUTOIP_CREATE_SEED_ADDR
#define LWIP_AUTOIP_CREATE_SEED_ADDR(netif) \
    htonl(AUTOIP_RANGE_START + ((u32_t)(((u8_t)(netif->hwaddr[4])) | \
                                        ((u32_t)((u8_t)(netif->hwaddr[5]))) << 8)))
#endif /* LWIP_AUTOIP_CREATE_SEED_ADDR */

/* static functions */
static void autoip_handle_arp_conflict(struct netif *netif);

/* creates a pseudo random LL IP-Address for a network interface */
static void autoip_create_addr(struct netif *netif, struct ip_addr *ipaddr);

/* sends an ARP probe */
static err_t autoip_arp_probe(struct netif *netif);

/* sends an ARP announce */
static err_t autoip_arp_announce(struct netif *netif);

/* configure interface for use with current LL IP-Address */
static err_t autoip_bind(struct netif *netif);

/* start sending probes for llipaddr */
static void autoip_start_probing(struct netif *netif);

/**
 * Initialize this module
 */
void
autoip_init(void)
{
    LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE, ("autoip_init()\n"));
}

/**
 * Handle a IP address conflict after an ARP conflict detection
 */
static void
autoip_handle_arp_conflict(struct netif *netif)
{
    /* Somehow detect if we are defending or retreating */
    unsigned char defend = 1; /* tbd */

    if (defend)
    {
        if (netif->autoip->lastconflict > 0)
        {
            /* retreat, there was a conflicting ARP in the last
             * DEFEND_INTERVAL seconds
             */
            LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
                        ("autoip_handle_arp_conflict(): we are defending, but in DEFEND_INTERVAL, retreating\n"));

            /* TODO: close all TCP sessions */
            autoip_start(netif);
        }
        else
        {
            LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
                        ("autoip_handle_arp_conflict(): we are defend, send ARP Announce\n"));
            autoip_arp_announce(netif);
            netif->autoip->lastconflict = DEFEND_INTERVAL * AUTOIP_TICKS_PER_SECOND;
        }
    }
    else
    {
        LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
                    ("autoip_handle_arp_conflict(): we do not defend, retreating\n"));
        /* TODO: close all TCP sessions */
        autoip_start(netif);
    }
}

/**
 * Create an IP-Address out of range 169.254.1.0 to 169.254.254.255
 *
 * @param netif network interface on which create the IP-Address
 * @param ipaddr ip address to initialize
 */
static void
autoip_create_addr(struct netif *netif, struct ip_addr *ipaddr)
{
    /* Here we create an IP-Address out of range 169.254.1.0 to 169.254.254.255
     * compliant to RFC 3927 Section 2.1
     * We have 254 * 256 possibilities */

    u32_t addr = ntohl(LWIP_AUTOIP_CREATE_SEED_ADDR(netif));

    addr += netif->autoip->tried_llipaddr;
    addr = AUTOIP_NET | (addr & 0xffff);
    /* Now, 169.254.0.0 <= addr <= 169.254.255.255 */

    if (addr < AUTOIP_RANGE_START)
    {
        addr += AUTOIP_RANGE_END - AUTOIP_RANGE_START + 1;
    }
    if (addr > AUTOIP_RANGE_END)
    {
        addr -= AUTOIP_RANGE_END - AUTOIP_RANGE_START + 1;
    }
    LWIP_ASSERT("AUTOIP address not in range", (addr >= AUTOIP_RANGE_START) &&
                (addr <= AUTOIP_RANGE_END));
    ipaddr->addr = htonl(addr);

    LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
                ("autoip_create_addr(): tried_llipaddr=%"U16_F ", 0x%08"X32_F "\n",
                 (u16_t)(netif->autoip->tried_llipaddr), (u32_t)(ipaddr->addr)));
}

/**
 * Sends an ARP probe from a network interface
 *
 * @param netif network interface used to send the probe
 */
static err_t
autoip_arp_probe(struct netif *netif)
{
    return etharp_raw(netif, (struct eth_addr *)netif->hwaddr, &ethbroadcast,
                      (struct eth_addr *)netif->hwaddr, IP_ADDR_ANY, &ethzero,
                      &netif->autoip->llipaddr, ARP_REQUEST);
}

/**
 * Sends an ARP announce from a network interface
 *
 * @param netif network interface used to send the announce
 */
static err_t
autoip_arp_announce(struct netif *netif)
{
    return etharp_raw(netif, (struct eth_addr *)netif->hwaddr, &ethbroadcast,
                      (struct eth_addr *)netif->hwaddr, &netif->autoip->llipaddr, &ethzero,
                      &netif->autoip->llipaddr, ARP_REQUEST);
}

/**
 * Configure interface for use with current LL IP-Address
 *
 * @param netif network interface to configure with current LL IP-Address
 */
static err_t
autoip_bind(struct netif *netif)
{
    struct autoip *autoip = netif->autoip;
    struct ip_addr sn_mask, gw_addr;

    LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
                ("autoip_bind(netif=%p) %c%c%"U16_F " 0x%08"X32_F "\n",
                 (void*)netif, netif->name[0], netif->name[1], (u16_t)netif->num, autoip->llipaddr.addr));

    IP4_ADDR(&sn_mask, 255, 255, 0, 0);
    IP4_ADDR(&gw_addr, 0, 0, 0, 0);

    netif_set_ipaddr(netif, &autoip->llipaddr);
    netif_set_netmask(netif, &sn_mask);
    netif_set_gw(netif, &gw_addr);

    /* bring the interface up */
    netif_set_up(netif);

    return ERR_OK;
}

/**
 * Start AutoIP client
 *
 * @param netif network interface on which start the AutoIP client
 */
err_t
autoip_start(struct netif *netif)
{
    struct autoip *autoip = netif->autoip;
    err_t result = ERR_OK;

    if (netif_is_up(netif))
    {
        netif_set_down(netif);
    }

    /* Set IP-Address, Netmask and Gateway to 0 to make sure that
     * ARP Packets are formed correctly
     */
    netif->ip_addr.addr = 0;
    netif->netmask.addr = 0;
    netif->gw.addr      = 0;

    LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
                ("autoip_start(netif=%p) %c%c%"U16_F "\n", (void*)netif, netif->name[0],
                 netif->name[1], (u16_t)netif->num));
    if (autoip == NULL)
    {
        /* no AutoIP client attached yet? */
        LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
                    ("autoip_start(): starting new AUTOIP client\n"));
        autoip = mem_malloc(sizeof(struct autoip));
        if (autoip == NULL)
        {
            LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
                        ("autoip_start(): could not allocate autoip\n"));
            return ERR_MEM;
        }
        memset( autoip, 0, sizeof(struct autoip));
        /* store this AutoIP client in the netif */
        netif->autoip = autoip;
        LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE, ("autoip_start(): allocated autoip"));
    }
    else
    {
        autoip->state = AUTOIP_STATE_OFF;
        autoip->ttw = 0;
        autoip->sent_num = 0;
        memset(&autoip->llipaddr, 0, sizeof(struct ip_addr));
        autoip->lastconflict = 0;
    }

    autoip_create_addr(netif, &(autoip->llipaddr));
    autoip->tried_llipaddr++;
    autoip_start_probing(netif);

    return result;
}

static void
autoip_start_probing(struct netif *netif)
{
    struct autoip *autoip = netif->autoip;

    autoip->state = AUTOIP_STATE_PROBING;
    autoip->sent_num = 0;

    /* time to wait to first probe, this is randomly
     * choosen out of 0 to PROBE_WAIT seconds.
     * compliant to RFC 3927 Section 2.2.1
     */
    autoip->ttw = (u16_t)(LWIP_AUTOIP_RAND(netif) % (PROBE_WAIT * AUTOIP_TICKS_PER_SECOND));

    /*
     * if we tried more then MAX_CONFLICTS we must limit our rate for
     * accquiring and probing address
     * compliant to RFC 3927 Section 2.2.1
     */
    if (autoip->tried_llipaddr > MAX_CONFLICTS)
    {
        autoip->ttw = RATE_LIMIT_INTERVAL * AUTOIP_TICKS_PER_SECOND;
    }
}

/**
 * Handle a possible change in the network configuration.
 *
 * If there is an AutoIP address configured, take the interface down
 * and begin probing with the same address.
 */
void
autoip_network_changed(struct netif *netif)
{
    if (netif->autoip && netif->autoip->state != AUTOIP_STATE_OFF)
    {
        netif_set_down(netif);
        autoip_start_probing(netif);
    }
}

/**
 * Stop AutoIP client
 *
 * @param netif network interface on which stop the AutoIP client
 */
err_t
autoip_stop(struct netif *netif)
{
    netif->autoip->state = AUTOIP_STATE_OFF;
    netif_set_down(netif);
    return ERR_OK;
}

/**
 * Has to be called in loop every AUTOIP_TMR_INTERVAL milliseconds
 */
void
autoip_tmr()
{
    struct netif *netif = netif_list;

    /* loop through netif's */
    while (netif != NULL)
    {
        /* only act on AutoIP configured interfaces */
        if (netif->autoip != NULL)
        {
            if (netif->autoip->lastconflict > 0)
            {
                netif->autoip->lastconflict--;
            }

            LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
                        ("autoip_tmr() AutoIP-State: %"U16_F ", ttw=%"U16_F "\n",
                         (u16_t)(netif->autoip->state), netif->autoip->ttw));

            switch (netif->autoip->state)
            {
            case AUTOIP_STATE_PROBING:
                if (netif->autoip->ttw > 0)
                {
                    netif->autoip->ttw--;
                }
                else
                {
                    if (netif->autoip->sent_num >= PROBE_NUM)
                    {
                        netif->autoip->state = AUTOIP_STATE_ANNOUNCING;
                        netif->autoip->sent_num = 0;
                        netif->autoip->ttw = ANNOUNCE_WAIT * AUTOIP_TICKS_PER_SECOND;
                    }
                    else
                    {
                        autoip_arp_probe(netif);
                        LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
                                    ("autoip_tmr() PROBING Sent Probe\n"));
                        netif->autoip->sent_num++;
                        /* calculate time to wait to next probe */
                        netif->autoip->ttw = (u16_t)((LWIP_AUTOIP_RAND(netif) %
                                                      ((PROBE_MAX - PROBE_MIN) * AUTOIP_TICKS_PER_SECOND) ) +
                                                     PROBE_MIN * AUTOIP_TICKS_PER_SECOND);
                    }
                }
                break;

            case AUTOIP_STATE_ANNOUNCING:
                if (netif->autoip->ttw > 0)
                {
                    netif->autoip->ttw--;
                }
                else
                {
                    if (netif->autoip->sent_num == 0)
                    {
                        /* We are here the first time, so we waited ANNOUNCE_WAIT seconds
                         * Now we can bind to an IP address and use it.
                         *
                         * autoip_bind calls netif_set_up. This triggers a gratuitous ARP
                         * which counts as an announcement.
                         */
                        autoip_bind(netif);
                    }
                    else
                    {
                        autoip_arp_announce(netif);
                        LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
                                    ("autoip_tmr() ANNOUNCING Sent Announce\n"));
                    }
                    netif->autoip->ttw = ANNOUNCE_INTERVAL * AUTOIP_TICKS_PER_SECOND;
                    netif->autoip->sent_num++;

                    if (netif->autoip->sent_num >= ANNOUNCE_NUM)
                    {
                        netif->autoip->state = AUTOIP_STATE_BOUND;
                        netif->autoip->sent_num = 0;
                        netif->autoip->ttw = 0;
                    }
                }
                break;
            }
        }
        /* proceed to next network interface */
        netif = netif->next;
    }
}

/**
 * Handles every incoming ARP Packet, called by etharp_arp_input.
 *
 * @param netif network interface to use for autoip processing
 * @param hdr Incoming ARP packet
 */
void
autoip_arp_reply(struct netif *netif, struct etharp_hdr *hdr)
{
    LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE, ("autoip_arp_reply()\n"));
    if ((netif->autoip != NULL) && (netif->autoip->state != AUTOIP_STATE_OFF))
    {
        /* when ip.src == llipaddr && hw.src != netif->hwaddr
         *
         * when probing  ip.dst == llipaddr && hw.src != netif->hwaddr
         * we have a conflict and must solve it
         */
        struct ip_addr sipaddr, dipaddr;
        struct eth_addr netifaddr;
        netifaddr.addr[0] = netif->hwaddr[0];
        netifaddr.addr[1] = netif->hwaddr[1];
        netifaddr.addr[2] = netif->hwaddr[2];
        netifaddr.addr[3] = netif->hwaddr[3];
        netifaddr.addr[4] = netif->hwaddr[4];
        netifaddr.addr[5] = netif->hwaddr[5];

        /* Copy struct ip_addr2 to aligned ip_addr, to support compilers without
         * structure packing (not using structure copy which breaks strict-aliasing rules).
         */
        SMEMCPY(&sipaddr, &hdr->sipaddr, sizeof(sipaddr));
        SMEMCPY(&dipaddr, &hdr->dipaddr, sizeof(dipaddr));

        if ((netif->autoip->state == AUTOIP_STATE_PROBING) ||
            ((netif->autoip->state == AUTOIP_STATE_ANNOUNCING) &&
             (netif->autoip->sent_num == 0)))
        {
            /* RFC 3927 Section 2.2.1:
             * from beginning to after ANNOUNCE_WAIT
             * seconds we have a conflict if
             * ip.src == llipaddr OR
             * ip.dst == llipaddr && hw.src != own hwaddr
             */
            if ((ip_addr_cmp(&sipaddr, &netif->autoip->llipaddr)) ||
                (ip_addr_cmp(&dipaddr, &netif->autoip->llipaddr) &&
                 !eth_addr_cmp(&netifaddr, &hdr->shwaddr)))
            {
                LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE | LWIP_DBG_LEVEL_WARNING,
                            ("autoip_arp_reply(): Probe Conflict detected\n"));
                autoip_start(netif);
            }
        }
        else
        {
            /* RFC 3927 Section 2.5:
             * in any state we have a conflict if
             * ip.src == llipaddr && hw.src != own hwaddr
             */
            if (ip_addr_cmp(&sipaddr, &netif->autoip->llipaddr) &&
                !eth_addr_cmp(&netifaddr, &hdr->shwaddr))
            {
                LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE | LWIP_DBG_LEVEL_WARNING,
                            ("autoip_arp_reply(): Conflicting ARP-Packet detected\n"));
                autoip_handle_arp_conflict(netif);
            }
        }
    }
}

#endif /* LWIP_AUTOIP */
